EDITORIAL Repolarization Reserve and Action Potential Dynamics in Failing Myocytes See Article by Hegyi et al Ji-Dong Fu, PhD Kenneth R. Laurita, PhD rolongation of action potential duration (APD) is typically observed in iso- lated myocytes from both humans and animals with heart failure (HF) and Pis generally thought to be an important arrhythmia substrate. Traditionally, + 2+ voltage-clamp studies have found that in addition to increased Na /Ca exchange + + and late Na currents, repolarizing currents, including the inward rectifier K (I ) K1 + 1,2 and delayed rectifier K (I , I ) currents, are decreased in HF. These changes Ks Kr are expected to significantly prolong repolarization; however, this is not often ob- 3 4 served at faster beating rates in failing myocytes and HF patients. In this issue of the Journal, Hegyi et al contend that more physiological conditions are required to understand the mechanisms of repolarization dynamics in HF myocytes. To this end, they used an elegant action potential (AP)–clamp technique to unravel the + 6 role and regulation of K currents under more realistic physiological conditions. Hegyi et al report that when more realistic physiological conditions are used 2+ by leaving Ca cycling
Circulation: Arrhythmia & Electrophysiology – Wolters Kluwer Health
Published: Feb 1, 2018
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